The present invention relates generally to control of robotic systems, and more particularly but not exclusively, to closed loop control for soldering systems.
For some arrangements and configurations of semiconductor devices disposed on printed circuit board assemblies, formed bus bars and the like, the use of soldered joints provide mechanical and electrical interconnection. One tool for making such solder joints is a selective wave soldering station. This tool includes a mobile solder pot controlled in three-dimensions to locate a standing solder wave at each solder joint location such that solder contact is made at the target joint location.
It is not uncommon to have relatively large arrays of devices, and in such a context the conventional selective wave soldering solution is not always able to easily control a vertical position of each solder joint within a sufficient level of precision to allow repeatable solder joints.
As an exemplary embodiment, a specific workpiece referred to herein as a formed bus bar is described. While the present invention is applicable to other workpieces, the particulars of the formed bus bar are useful in efficiently and clearly detailing problems addressed, and representative solutions enabled, by the present invention. Additional details of the formed bus bar may be found in U.S. patent application Ser. No. 13/149,532 filed 31 May 2011 entitled “POWER ELECTRONICS INTERCONNECTION FOR ELECTRIC MOTOR DRIVES” the contents of which are hereby expressly incorporated in its entirety by reference thereto for all purposes.
The formed bus bar of the incorporated patent application includes a relatively large array of insulated gate bipolar transistor (IGBT) devices interconnected to a three-layer bus bar. These bus bars may have height deviations that can cause solder joint locations to vary widely. Using a conventional selective wave soldering solution on such a formed bus bar is problematic as solder joint location is not tightly controlled in wave height.
What is needed is an apparatus and method for controlling fine positioning in a robotic electronic array processor, particularly vertical positioning for a selective wave soldering station.